(a) Field of the Invention
The present invention relates to a communication device, a multicast control method, and a scheduling control method.
(b) Description of the Related Art
Network coding is a technique which allows a relay node to code multiple packets by linear coupling or an exclusive OR operation (XOR) and forward them, and a receiving node to decode a coded signal and receive the packets during a packet transfer process.
One of the simplest examples is DAF (decode-and-forward) two-way relaying. DAF is applicable when two nodes exchange data.
According to DAF, two nodes, i.e., node A and node B, in a network send data. Relay node R relays between node A and node B.
First, node A sends packet X to relay node R. Then, node B sends packet Y to relay node R. Node A and node B store the packet X and packet Y they have sent in local buffers.
Hereupon, relay node R linearly couples the received packet X and packet Y and at the same time forwards them to node A and node B. Node A and node B decode and receive packet X and packet Y, respectively, using the packet X and the packet Y which have been stored in their local buffers.
However, there is a limitation that the conventional DAF can be applied only when two nodes in a multi-hop network send and receive data in a linear phase.
When using multicasting without network coding in a multi-hop network in the conventional art, packet transmission occurs as follows.
1) node 1 transmits packet (a) to node 2 and node 3, respectively, which are connected to it.
2) node 4 transmits packet (b) to node 3 which is connected to it.
3) node 3 transmits packet (a) to node 4.
4) node 3 transmits packet (b) to node 1 and node 2.
In this way, packet transmission is carried out in four stages in the conventional art.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.